This is true for Healthcare users who are trying to share their calendar with Office 365 users also. The user will not be able to edit the calendar though.
Healthcare users will only be able to see the free/busy information of the Office 365 users. Office 365 users will only be able to share detailed calendar information with other Office 365 users.Publishing: this options allows you to publish a calendar for use on a web page, for a non-Office365 user to see, etc. Sharing: this option allows you to specify who can view your calendar, the details they can see and if they have editing or delegate rights. Giving Permissions: this option allows you to specify who can view your calendar, the details they can see and if they have editing rights. NOTE: if you are trying to share a resource, see Office 365 Resource Management There are several options for sharing your personal calendar with other users - sharing, publishing, giving permissions.
